So I've been making AMVs for a while now, but I've recently run into problems with converting certain MKVs to AVI. On some of these files, there's really bad pixelation, but only when converting it. When I view it in Media Player Classic, the video plays fine, but when I try to convert it, whether using a program converter like Aiseesoft MKV Converter or with AvsPmod/VirtualDub it becomes really pixelated. Here's an example:

Spoiler :

I don't think this is quality loss due to compression, because it's like this before I even compresses it; it's already pixelated on the virtualdub interface when I open it. Here are the specs of the video I'm using (via MediaInfo).

I have no idea why some MKVs convert fine and some come out horribly pixelated (and all of them play fine in Media player classic). I'm very noobish when it comes to these things though, so can anybody tell me why this is happening? The codec I'm using is K-Lite Mega pack, by the way. Needless to day, this is becoming really annoying. Thanks in advance! ^^